Electrochemical and electrical equipment

Abstract

To provide an electrochemical device and an electrical appliance for extending the service life of the electrochemical device. [Solution] The electrochemical device includes a case and a wound electrode assembly, the electrode assembly is housed in the case, the electrode assembly has a winding center line, the electrode assembly includes positive electrode pieces and negative electrode pieces, along the winding direction of the positive electrode pieces, the positive electrode active material layer of the positive electrode pieces includes a positive electrode winding starting end and a positive electrode winding ending end, a line that passes through the positive electrode winding ending end and is perpendicular to the winding center line is taken as a first reference line, a line that is perpendicular to the first reference line and perpendicular to the winding center line is taken as a second reference line, and a line that passes through the positive electrode winding starting end and is perpendicular to the winding center line is taken as a third reference line, the third reference line and the second reference line form a zero angle or acute angle α, satisfying 0°≦α≦30°.

Description

[Technical Field]

[0001] This application relates to the field of battery technology, and in particular to electrochemical devices and electrical appliances. [Background technology]

[0002] With the rapid development of fields such as portable electronic devices, electric vehicles, power tools, drones, and energy storage devices, the requirements for the service life of batteries therein are becoming increasingly higher. Summary of the Invention

[0003] The present application provides electrochemical devices and electrical equipment to extend the service life of electrochemical devices.

[0004] In a first aspect, the present application provides an electrochemical device including a case and a wound electrode assembly, wherein a storage space is formed inside the case, the wound electrode assembly is stored in the storage space, the wound electrode assembly has a winding center line, the wound electrode assembly includes positive electrode pieces and negative electrode pieces, the positive electrode pieces include a positive electrode active material layer, the positive electrode active material layer has a positive electrode winding start end and a positive electrode winding end along the winding direction of the positive electrode pieces, when viewed along the winding center line, a first reference line is a line that passes through the positive electrode winding end end and is perpendicular to the winding center line, a second reference line is a line that is perpendicular to the first reference line and is perpendicular to the winding center line, and a third reference line is a line that passes through the positive electrode winding start end and is perpendicular to the winding center line, the third reference line and the second reference line form a zero angle or acute angle α, satisfying 0°≦α≦30°.

[0005] The inventors of the present application found that when an electrochemical device is charged, the electrode pieces expand in volume. Because the curvature of the inner circumference of the winding is small, a large change in the radius of the inner circumference of the winding is required for the same volume expansion. However, the radius change of the inner circumference of the winding is limited, resulting in inward radial pressure. This situation could easily cause the electrode pieces at the inner circumference of the winding to become depressed, affecting the service life of the electrochemical device. Because the wound electrode assembly has an involute wire structure, the diameter is largest at the first reference line, and the inward radial pressure is also largest. During cycling, the electrode assembly tends to deform along the second reference line, forming an ellipse. In the present application, the zero or acute angle α between the third and second reference lines is set to satisfy the range of 0°≦α≦30°, and the positive electrode winding start end of the positive electrode active material layer is set close to the second reference line. The second reference line is located near the long axis of the ellipse, and has a small curvature at the end of the long axis of the ellipse, and can withstand a large pressure, thereby preventing the pole piece from failing due to depression at the winding start end. On the other hand, the positive electrode winding start end is located near the end of the long axis of the ellipse, and can effectively perform its arched supporting role, allowing the pole piece on the inner circumference of the winding to withstand a larger radial pressure along the direction of the first reference line, thereby preventing the pole piece on the inner circumference of the winding from depression and reducing the risk of failure due to depression of the pole piece on the inner circumference of the winding of the electrochemical device, thereby contributing to extending the service life of the electrochemical device.

[0006] In some embodiments, 0°≦α≦25°. In this case, the positive electrode winding start end of the positive electrode active material layer is positioned closer to the second reference line, which can better prevent malfunction due to depression of the pole piece winding start end, while better supporting the pole piece on the inner circumference of the winding, further preventing depression of the pole piece on the inner circumference of the winding, and extending the service life of the electrochemical device. Furthermore, in some embodiments, 0°≦α≦10°.

[0007] In some embodiments, the wound electrode assembly has a central hole, the radius of the central hole is r, and the radius of the wound electrode assembly is R, where r≧0.15R. In this case, when the inner circumference of the winding is subjected to radial pressure, a sufficient buffer space is provided, which can further prevent the pole pieces on the inner circumference of the winding from being depressed.

[0008] In some embodiments, r≧0.3R, which provides a larger buffer space when the inner circumference of the winding is subjected to radial pressure, thereby further reducing the risk of depression of the pole pieces of the inner circumference of the winding.

[0009] In some embodiments, r≦0.5R. In this case, it is possible to avoid a decrease in the energy density of the electrochemical device due to an excessively large radius of the central hole for winding.

[0010] In some embodiments, r≧1 mm, which provides sufficient space for the central hole of the winding, reduces the risk of denting of the pole pieces on the inner circumference of the winding, and also contributes to sufficient infiltration of the electrolyte into the wound electrode assembly, thereby contributing to the full utilization of the capacity of the electrochemical device.

[0011] In some embodiments, the negative electrode piece includes a negative electrode active material layer, the negative electrode active material layer having a negative electrode winding end and a negative electrode winding start end, and the negative electrode winding end exceeds the positive electrode winding end along the winding direction of the wound electrode assembly.

[0012] In some embodiments, the negative electrode winding start end extends beyond the positive electrode winding start end along the opposite winding direction of the wound electrode assembly.

[0013] In the above technical solution, if the winding end of the negative electrode exceeds the winding end of the positive electrode and / or the winding start of the negative electrode exceeds the winding start of the positive electrode, the positive electrode active material layer will be sufficiently covered by the negative electrode active material layer, reducing the risk of lithium deposition in the electrochemical device and thereby improving the safety of the electrochemical device.

[0014] In some embodiments, the length by which the negative electrode winding end exceeds the positive electrode winding end is 1 mm or more along the winding direction of the wound electrode assembly, which contributes to sufficient coverage of the positive electrode active material layer by the negative electrode active material layer and reduces the risk of lithium deposition in the electrochemical device.

[0015] In some embodiments, the length by which the negative electrode winding start end extends beyond the positive electrode winding start end in the direction opposite to the winding direction of the wound electrode assembly is 1 mm or more, which contributes to sufficient coverage of the positive electrode active material layer by the negative electrode active material layer and reduces the risk of lithium deposition in the electrochemical device.

[0016] In some embodiments, the outermost electrode piece of the wound electrode assembly is the negative electrode piece, and / or the innermost electrode piece of the wound electrode assembly is the negative electrode piece, which contributes to the positive electrode piece of the wound electrode assembly being sufficiently covered by the negative electrode piece, thereby further reducing the risk of lithium deposition in the electrochemical device.

[0017] In some embodiments, the case includes a lid, side walls, and a bottom wall, the side walls being cylindrical, the electrochemical device further includes an electrode terminal and a positive current collecting member, the wound electrode assembly includes a positive electrode tab, the electrode terminal is installed on the lid and electrically connected to the positive electrode tab via the positive electrode current collecting member. In the above technical solution, the electrode terminal and the positive electrode tab are electrically connected via the positive electrode current collecting member, which contributes to improving the stability of the electrical connection between the electrode terminal and the positive electrode tab.

[0018] In some embodiments, the electrochemical device further includes a negative current collecting member, the wound electrode assembly includes a negative tab, and the bottom wall is electrically connected to the negative tab via the negative current collecting member. In the above technical solution, the bottom wall and the negative tab are electrically connected via the negative current collecting member, which contributes to improving the stability of the electrical connection between the negative terminal and the negative tab.

[0019] In some embodiments, the case includes a lid, sidewalls, and a bottom wall, the sidewalls being cylindrical, the electrochemical device further including an electrode terminal and a positive current collecting member, the positive electrode piece further including a positive current collector, the positive current collector including a positive electrode coating area and a positive electrode tab area, the positive electrode tab area being located at one widthwise end of the positive electrode current collector, the positive electrode active material layer being disposed on the surface of the positive electrode coating area, the positive electrode tab area being bent toward the winding centerline to form a first end face of the wound electrode assembly, the electrode terminal being disposed on the lid and electrically connected to the first end face via the positive electrode current collecting member. In the above technical solution, the electrode terminal being disposed on the lid and connected to the first end face via the positive electrode current collecting member contributes to increasing the contact area between the positive electrode current collecting member and the positive electrode piece, thereby improving the rate performance of the electrochemical device.

[0020] In some embodiments, the electrochemical device includes a negative electrode active material layer and a negative electrode current collecting member, the negative electrode piece further includes a negative electrode current collector, the negative electrode current collector includes a negative electrode coating region and a negative electrode tab region, the negative electrode tab region is located at one widthwise end of the negative electrode current collector, the negative electrode active material layer is disposed on the surface of the negative electrode coating region, the negative electrode tab region is bent toward the winding centerline to form a second end face of the wound electrode assembly, and the bottom wall is connected to the second end face via the negative electrode current collecting member. In the above technical solution, the bottom wall is connected to the second end face via the negative electrode current collecting member, which contributes to increasing the connection area between the negative electrode current collecting member and the negative electrode piece, thereby improving the rate performance of the electrochemical device.

[0021] In a second aspect, the present application provides an electrical appliance including an electrochemical device as provided in any embodiment of the first aspect. [Brief explanation of the drawings]

[0022] In order to more clearly explain the technical solutions of the embodiments of the present application, the following will briefly describe the drawings necessary for the embodiments. However, it should be understood that the following drawings only illustrate some embodiments of the present application and should not be considered as limiting the scope.

[0023] [Figure 1] FIG. 1 is a comparison diagram of the central hole of the electrode assembly before and after expansion.

[0024] [Figure 2] FIG. 2 is a schematic diagram of an electrochemical device provided in some embodiments of the present application.

[0025] [Figure 3] FIG. 3 is a schematic diagram of the configuration of an electrochemical device provided in some other embodiments of the present application.

[0026] [Figure 4] FIG. 4 is a schematic diagram of the configuration of an electrochemical device provided in some other embodiments of the present application.

[0027] [Figure 5] FIG. 5 is an exploded view of an electrochemical device provided in some embodiments of the present application.

[0028] [Figure 6] FIG. 6 is an exploded view of an electrochemical device provided in some other embodiments of the present application.

[0029] [Figure 7] FIG. 7 is an exploded view of an electrochemical device provided in some other embodiments of the present application.

[0030] [Figure 8] FIG. 8 is an exploded view of an electrochemical device provided in some other embodiments of the present application.

[0031] [Figure 9] Figure 9 shows CT images of a base cylindrical steel case lithium-ion battery with α = 45° after cycling.

[0032] Reference numerals: 100', 100... electrochemical device, 10', 10... case, 11... lid, 12... side wall, 121... opening, 13... bottom wall, 20', 20... wound electrode assembly, 21', 21... positive electrode piece, 211', 211... positive electrode active material layer, 2111', 2111... positive electrode winding start end, 2 112', 2112... Positive electrode winding end, 212... Positive electrode current collector, 2121... Positive electrode coating area, 2122... Positive electrode tab area, 2123... First end surface, 22', 22... Negative electrode piece, 221', 221... Negative electrode active material layer, 2211', 2211... Negative electrode winding start end, 2212', 2212... Negative electrode Winding end end, 222... negative electrode current collector, 2221... negative electrode coating area, 2222... negative electrode tab area, 2223... second end surface, 23', 23... separator, 24... winding center hole, 24a... winding center hole before deformation, 24b... winding center hole after deformation, 25... positive electrode tab, 26... negative electrode tab, 40... ··Electrode terminal, 50···Positive electrode current collecting member, 60···Negative electrode current collecting member, A···First position, B···Second position, C···Third position, D···Fourth position, E1···Fifth position, E2···Sixth position, F1···Winding center line, F2···First reference line, F3···Second reference line, F4···Third reference line, X···Winding direction. DETAILED DESCRIPTION OF THE INVENTION

[0033] In order to make the objectives, technical solutions and advantages of the present application clearer, the technical solutions in the embodiments of the present application will be clearly and in detail described below with reference to the drawings in the embodiments of the present application. Of course, the described embodiments are only a part of the embodiments of the present invention, but not all of the embodiments.

[0034] It should be noted that the embodiments and features of the embodiments of the present application can be combined with each other as long as they do not interfere with each other.

[0035] It should be noted that in the following drawings, like numerals and symbols represent like items, so that if an item is defined in one drawing, no further definition or interpretation thereof is required in subsequent drawings.

[0036] In the description of the embodiments of the present application, the orientations or positional relationships shown are those shown in the drawings, those that are typically used when using the product of the present application, or those that would be commonly understood by a person skilled in the art. These orientations or positional relationships are intended to facilitate and simplify the description of the present application, and do not necessarily indicate or suggest that the devices or elements shown necessarily have a specific orientation, or that they are arranged or operated in a specific orientation. Therefore, these orientations or positional relationships should not be understood as limitations on the present application. Furthermore, the terms "first," "second," "third," etc. are used for the purpose of distinction and do not indicate or suggest relative importance.

[0037] As shown in FIG. 1 , the electrochemical device 100′ includes a case 10′ and a wound electrode assembly 20′, which is housed in the case 10′. The electrode assembly 20′ includes a positive electrode piece 21′, a negative electrode piece 22′, and a separator 23′. The separator 23′ is positioned between the positive electrode piece 21′ and the negative electrode piece 22′ to separate the positive electrode piece 21′ from the negative electrode piece 22′. The electrochemical device 100′ is charged and discharged by the movement of metal ions between the positive electrode piece 21′ and the negative electrode piece 22′. To ensure the safety of the electrochemical device, the negative electrode winding end 2212′ of the negative electrode active material layer 221′ of the negative electrode piece 22′ extends beyond the positive electrode winding end 2112′ of the positive electrode active material layer 211′ of the positive electrode piece 21′ along the winding direction X. In the region from the positive electrode winding end 2112' to the negative electrode winding end 2212', there is a gap between the outermost part of the electrode assembly 20' and the case 10'. The wound electrode assembly 20' includes a wound electrode assembly that is cylindrical, and the shape of the case 10' may match the shape of the electrode assembly. For example, if the electrode assembly is cylindrical, the case 10' is cylindrical.

[0038] The inventors have conducted research and found the following: Unlike the electrochemical device 100', which has a cylindrical wound electrode assembly 20', the negative electrode piece 22' of the electrochemical device 100' expands during charging due to the absorption of metal ions. Because the curvature of the inner circumference of the winding is small, the change in radius of the inner circumference of the winding is large for the same volume expansion. However, because the change in radius of the inner circumference of the winding is limited, inward radial pressure occurs. If this continues, the electrode piece at the inner circumference of the winding is likely to become depressed, which will affect the service life of the electrochemical device 100'. Furthermore, because the wound electrode assembly 20' has an involute wire structure, the diameter at the positive electrode winding end 2112' is the largest, and the inward radial pressure is also the largest. If the case 10' is also cylindrical, the electrode assembly 20' expands during cycling. A first position A, which corresponds to the outermost positive electrode winding end 2112' of the electrode assembly 20', and a second position B, which is located in the same radial direction as the first position A, initially contact the inner wall of the case 10'. The case 10' applies a radial pressure to the first position A and the second position B toward the winding center line F1. This causes the circular winding center hole 24 of the electrode assembly (i.e., the winding center hole 24a before deformation in FIG. 1) to gradually change into an elliptical winding center hole 24 (i.e., the winding center hole 24b after deformation in FIG. 1). The minor axis of the elliptical winding center hole 24b is aligned with the line connecting the first position A and the second position B, and the major axis of the elliptical winding center hole 24b is aligned with the line connecting the third position C and the fourth position D.

[0039] Based on the above considerations, the inventors have made extensive studies to alleviate the failure of the electrochemical device due to the dents in the electrode pieces and to extend the service life of the electrochemical device, and have provided an electrochemical device 100. As shown in Figures 2 to 4, the electrochemical device 100 includes a case 10 and a wound electrode assembly 20. A storage space is formed inside the case 10. The wound electrode assembly 20 is stored in the storage space. The wound electrode assembly 20 has a winding center line F1. The wound electrode assembly 20 includes a positive electrode piece 21 and a negative electrode piece 22. The positive electrode piece 21 includes a positive electrode active material layer 211. The positive electrode active material layer 211 is wound along the winding direction X of the positive electrode piece 21. The positive electrode active material layer 211 is wound around the positive electrode winding start end 212. 111 and positive electrode winding end 2112, and when viewed along the direction of winding center line F1, if a straight line that passes through positive electrode winding end 2112 and is perpendicular to winding center line F1 is defined as a first reference line F2, a straight line that is perpendicular to first reference line F2 and perpendicular to winding center line F1 is defined as a second reference line F3, and a straight line that passes through positive electrode winding starting end 2111 and is perpendicular to winding center line F1 is defined as a third reference line F4, then the third reference line F4 and the second reference line F3 form a zero angle or acute angle α, which satisfies 0°≦α≦30°.

[0040] By setting the third reference line F4 and the second reference line F3 so that they form a zero angle or an acute angle α and satisfy 0°≦α≦30°, the positive electrode winding starting end 2111 of the positive electrode active material layer 211 is set close to the second reference line F3. The second reference line F3 is located near the long axis of the deformed elliptical winding center hole, and the curvature at the long axis end point of the elliptical winding center hole is small and the withstand pressure is large, so that failure due to depression of the winding starting end of the pole piece can be suppressed. On the other hand, the positive electrode winding starting end 2111 is located near the long axis end point of the deformed elliptical winding center hole, and can effectively perform the arched supporting role, so that the pole piece on the inner circumference of the winding can withstand greater radial pressure along the direction of the first reference line F2, thereby suppressing depression of the pole piece on the inner circumference of the winding and reducing the risk of failure due to depression of the pole piece on the inner circumference of the winding of the electrochemical device 100, thereby contributing to extending the service life of the electrochemical device 100.

[0041] The case 10 may be cylindrical, and the axis of the case 10 may be parallel to the winding centerline F1 of the wound electrode assembly 20. In some embodiments, the axis of the case 10 may overlap the winding centerline F1 of the electrode assembly.

[0042] The electrode assembly 20 further includes a separator 23, and the positive electrode piece 21, the separator 23, and the negative electrode piece 22 are stacked and wound to form the wound electrode assembly 20. The separator 23 is used to separate the positive electrode piece 21 and the negative electrode piece 22. The material of the separator 23 may be polypropylene (PP), polyethylene (PE), or the like.

[0043] The electrochemical device 100 operates primarily through the movement of metal ions between the positive electrode piece 21 and the negative electrode piece 22. The positive electrode piece 21 includes a positive electrode active material layer 211 and a positive electrode current collector 212. The negative electrode piece 22 includes a negative electrode active material layer 221 and a negative electrode current collector 222. Taking a lithium-ion battery as an example, the material of the positive electrode current collector 212 may be aluminum, and the positive electrode active material may be lithium cobalt oxide, lithium iron phosphate, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminate, lithium manganese oxide, or the like. The material of the negative electrode current collector 222 may be copper, and the negative electrode active material may be carbon, silicon, or the like.

[0044] Positive electrode active material layers 211 are provided on both of two opposing surfaces of the positive electrode current collector 212 along the thickness direction of the positive electrode current collector 212. Negative electrode active material layers 221 are provided on both of two opposing surfaces of the negative electrode current collector 222 along the thickness direction of the negative electrode current collector 222.

[0045] The positive electrode winding starting end 2111 is the end along the winding direction X that is closest to the winding center line F1 of the positive electrode active material layer 211. The positive electrode winding ending end 2112 is the end along the winding direction X that is farthest from the winding center line F1 of the positive electrode piece 21.

[0046] 3, in some embodiments, the positions of the positive electrode winding end ends 2112 of the positive electrode active material layers 211 on the two surfaces in the thickness direction of the positive electrode current collector 212 of the positive electrode piece 21 may coincide. In this case, the first reference line F2 may be a straight line that passes through the positive electrode winding end end 2112 of one of the two positive electrode active material layers 211 and is perpendicular to the winding center line F1.

[0047] 4 , in some other embodiments, the positions of the positive electrode winding end ends 2112 of the positive electrode active material layers 211 on the two surfaces in the thickness direction of the positive electrode current collector 212 of the positive electrode piece 21 may not coincide, i.e., the positive electrode winding end end 2112 of one of the two positive electrode active material layers 211 extends beyond the positive electrode winding end 2112 of the other positive electrode active material layer 211 along the winding direction X. In other words, the positive electrode winding end end 2112 of one of the two positive electrode active material layers 211 is located in front of the other positive electrode winding end 2112 along the winding direction X. In this case, the first reference line F2 is a straight line that passes through the positive electrode winding end 2112 located rearward in the winding direction X (closer to the positive electrode winding start end 2111) and is perpendicular to the winding center line F1.

[0048] 3, in some embodiments, the positions of the positive electrode winding starting ends 2111 of the positive electrode active material layers 211 on the two surfaces in the thickness direction of the positive electrode current collector 212 of the positive electrode piece 21 may be the same. In this case, the third reference line F4 may be a straight line that passes through the positive electrode winding starting end 2111 of one of the two positive electrode active material layers 211 and is perpendicular to the winding center line F1.

[0049] 4 , in some other embodiments, the positions of the positive electrode winding starting ends 2111 of the positive electrode active material layers 211 on the two surfaces in the thickness direction of the positive electrode current collector 212 of the positive electrode piece 21 may not coincide, i.e., the positive electrode winding starting end 2111 of one of the two positive electrode active material layers 211 extends beyond the positive electrode winding starting end 2111 of the other positive electrode active material layer 211 along the reverse direction of the winding direction X. In other words, the positive electrode winding starting end 2111 of one of the two positive electrode active material layers 211 is located in front of the positive electrode winding starting end 2111 of the other positive electrode active material layer 211 along the reverse direction of the winding direction X. In this case, the third reference line F4 is a straight line that passes through the positive electrode winding starting end 2111 located rearward in the reverse direction of the winding direction X and is perpendicular to the winding center line F1.

[0050] In this embodiment, "orthogonal" may be understood as "perpendicular." Therefore, the first reference line F2 may be understood as a line that passes through the positive electrode winding end 2112 and is perpendicular to the winding center line F1. The second reference line F3 may be understood as a line that is perpendicular to the first reference line F2 and perpendicular to the winding center line F1. The third reference line F4 may be understood as a line that passes through the positive electrode winding start end 2111 and is perpendicular to the winding center line F1.

[0051] Table 1 shows the results of a cycle test on a cylindrical steel-cased lithium-ion battery, where the positive electrode material is LiNi0.5Co0.2Mn0.3O2, the negative electrode material is graphite, and the radius R of the wound electrode assembly is 5.5 mm.

[0052] The test data in Table 1 was obtained under the following test conditions: Under conditions of an ambient temperature of 20°C ± 5°C, in step A, the battery was charged at a fixed rate of 2C with a constant current. When the voltage reached the charging limit voltage of 4.2V, the charging current was reduced to a cut-off current of 0.05C, and the battery was then charged at a constant voltage of 4.2V, after which the battery was left for 5 minutes. Then, in step B, the battery was discharged at a constant current of 10C with a cut-off voltage of 2.8V. After 300 charge-discharge cycles in steps A and B, CT scan measurements were performed to evaluate the condition of pole tip depressions.

[0053] The degree of denting is classified as follows: Taking the winding centerline F1 as the reference and the radius of the initial winding center hole 24 as r, if the shortest distance from the pole piece to the winding centerline F1 after cycling is 0.9r to r, it is evaluated as not dented. If there is denting after cycling, but the shortest distance from the dented pole piece to the winding centerline F1 is a, if 0.7r≦a<0.9r, it is evaluated as slightly dented, if 0.5r≦a<0.7r, it is evaluated as moderately dented, and if 0≦a<0.5r, it is evaluated as severely dented. Table 1 shows cycle test data for winding configurations with different dimensions.

[0054] [Table 1]

[0055] As can be seen from Table 1 and Figure 9, under the same test conditions, when α is 45°, the pole piece recession is very severe. Compared to when α is 45°, in Examples 1 to 18, when α is ±30°, the pole piece recession is significantly improved, and when α is ±10°, the pole piece is not recessed. As a result, the degree of pole piece recession decreases as α becomes smaller.

[0056] The first end and the second end in Table 1 are two opposing intersections between the second reference line F3 and the wound electrode assembly 20. The third reference line F4 may be located on one side away from the second reference line F3 along the winding direction X, or on one side away from the second reference line F3 along the opposite direction of the winding direction X. That is, α may be a positive angle or a negative angle. That is, the third reference line F4 may be offset by a certain angle relative to the second reference line F3 in the winding direction X or in the opposite direction of the winding direction X. To test these two cases, +α and -α are used to distinguish between them.

[0057] In some embodiments, 0°≦α≦25°. Further, in some embodiments, 0°≦α≦10°.

[0058] Referring to Table 1, when α is ±30°, the pole piece recession situation is improved to some extent compared to when α is 45°, but the pole pieces are still moderately recessed. When α is ±25°, ±10°, or 0°, the pole pieces are only slightly recessed or not recessed at all, which greatly improves the structural stability of the wound electrode assembly and further extends the service life of the lithium ion battery.

[0059] In some embodiments, α may be 5°, 8°, 11°, 13°, 15°, 18°, etc.

[0060] When 0°≦α≦25°, the positive electrode winding starting end 2111 of the positive electrode active material layer 211 is positioned closer to the second reference line F3, which can better prevent failure due to depression of the pole piece winding starting end, while better supporting the pole piece on the inner circumference of the winding, further preventing depression of the pole piece on the inner circumference of the winding, and extending the service life of the electrochemical device 100.

[0061] In some embodiments, the wound electrode assembly 20 comprises a central wound hole 24, the radius of the central wound hole 24 is r, and the radius of the wound electrode assembly 20 is R, where r≧0.15R.

[0062] In this embodiment, the radius r of the winding center hole 24 may be equivalent to the radius of a circle whose perimeter is the same as the length of the innermost pole piece and whose center is the winding center line F1. The length of the innermost pole piece refers to the length from the starting end of the pole piece located at the innermost periphery to the position where it first aligns with the starting end along the winding direction X. For example, if the innermost periphery of the wound electrode assembly 20 is the negative electrode piece 22, the length of the innermost pole piece is the length from the negative electrode winding starting end 2211 of the negative electrode piece 22 to the position (fifth position E1 in the figure) where it first aligns with the negative electrode winding starting end 2211 in the radial direction of the wound electrode assembly 20 after winding along the winding direction X.

[0063] The radius R of the wound electrode assembly 20 may be equivalent to the radius of a circle whose perimeter is the same as the length of the outermost pole piece and whose center is the winding center line F1. The length of the outermost pole piece refers to the length of the portion from the end of the outermost pole piece to the position where it first aligns with the end end in the radial direction of the wound electrode assembly 20 along the opposite direction to the winding direction X (the sixth position E2 in the figure).

[0064] Next, referring to Table 1, in Examples 3 and 19 to 24, when r is 0.1R, the degree of pole piece recession is large, and compared to when r is 0.1R, when r is 0.15R and 0.2R, the pole piece is slightly recessed, but when r is 0.3R, 0.4R, 0.5R, and 0.6R, the pole piece is hardly recessed.

[0065] Therefore, the radius R of the wound electrode assembly 20 and the radius r of the winding center hole 24 of the wound electrode assembly 20 must satisfy r≧0.15R, so that the winding center hole 24 has sufficient space and provides sufficient buffering space when the inner circumference of the wound electrode assembly 20 is subjected to radial pressure, thereby providing a certain degree of buffering and further mitigating the depression of the pole pieces on the inner circumference of the winding.

[0066] Furthermore, r≧0.3R. As shown in Table 1, when r is 0.3R, 0.4R, 0.5R, or 0.6R, the pole pieces are hardly recessed.

[0067] Furthermore, r≦0.5R. As can be seen from Table 1, when r is 0.6R, the pole pieces are hardly recessed, but the space of the winding center hole 24 is too large, the space occupied inside the case 10 is large, and the energy density of the electrochemical device 100 is low.

[0068] In some embodiments, for example, r may be 0.45R, 0.35R, 0.25R, 0.18R, etc.

[0069] In some embodiments, r≧1 mm. For example, r may be 2 mm, 3 mm, 4 mm, 5 mm, etc. When r≧1 mm, the central hole 24 has sufficient space, reducing the risk of denting of the pole pieces at the inner circumference of the winding, and further contributing to the electrolyte sufficiently permeating the wound electrode assembly 20, thereby contributing to the full utilization of the capacity of the active material.

[0070] 2 to 4, the negative electrode piece 22 includes a negative electrode active material layer 221, and the negative electrode active material layer 221 has a negative electrode winding end 2212, and the negative electrode winding end 2212 extends beyond the positive electrode winding end 2112 along the winding direction X of the wound electrode assembly 20.

[0071] The negative electrode winding end 2212 refers to the end farthest from the winding center line F1 of the negative electrode active material layer 221 along the winding direction X, and specifically, it is the end farthest from the winding center of the negative electrode active material layer 221 along the winding direction X.

[0072] There is a distance between the negative electrode winding end 2212 and the positive electrode winding end 2112 along the winding direction X, and the negative electrode winding end 2212 is located in front of the positive electrode winding end 2112.

[0073] In an embodiment in which anode active material layers 221 are disposed on both of two surfaces of the anode current collector 222 of the anode piece 22 that face each other along the thickness direction, and cathode active material layers 211 are disposed on both of two surfaces of the cathode current collector 212 of the cathode piece 21 that face each other along the thickness direction, the anode winding end 2212 of each anode active material layer 221 may extend beyond the cathode winding end 2112 of the cathode active material layer 211 that faces the anode active material layer 221, with the separator 23 interposed between them, along the winding direction X.

[0074] When the negative electrode winding end 2212 of the negative electrode active material layer 221 extends beyond the positive electrode winding end 2112 of the positive electrode active material layer 211 along the winding direction X of the wound electrode assembly 20, this helps to ensure that the positive electrode active material layer 211 is sufficiently covered by the negative electrode active material layer 221, thereby reducing the risk of lithium deposition in the electrochemical device 100.

[0075] As shown in FIGS. 2 to 4, the length by which the negative electrode winding end 2212 extends beyond the positive electrode winding end 2112 along the winding direction X of the winding type electrode assembly 20 is 1 mm or more.

[0076] In other words, the length by which the negative electrode winding end 2212 of the negative electrode active material layer 221 exceeds the positive electrode winding end 2112 of the positive electrode active material layer 211, which is disposed facing the negative electrode active material layer 221 along the winding direction X, is 1 mm or more. That is, with respect to the distance H in the winding direction X between the negative electrode winding end 2212 of the negative electrode active material layer 221 and the positive electrode winding end 2112 of the positive electrode active material layer 211, which is disposed facing the negative electrode active material layer 221 across the separator 23, H≧1 mm. H may be 2 mm, 3 mm, 4 mm, 5 mm, etc.

[0077] If the length by which the negative electrode winding end 2212 exceeds the positive electrode winding end 2112 is 1 mm or more, this contributes to the positive electrode active material layer 211 being sufficiently covered by the negative electrode active material layer 221, and the risk of lithium deposition in the electrochemical device 100 can be reduced.

[0078] In some other embodiments, the positions of the negative electrode winding end 2212 and the positive electrode winding end 2112 may coincide.

[0079] 2 to 4, the negative electrode winding starting end 2211 extends beyond the positive electrode winding starting end 2111 in the direction opposite to the winding direction X of the wound electrode assembly 20.

[0080] The negative electrode winding starting end 2211 is located inside the positive electrode winding starting end 2111, i.e., along the radial direction of the wound electrode assembly 20, the distance between the negative electrode winding starting end 2211 and the winding center line F1 is smaller than the distance between the positive electrode winding starting end 2111 and the winding center line F1.

[0081] The negative electrode winding starting end 2211 is the end along the winding direction X that is closest to the winding center line F1 of the negative electrode active material layer 221.

[0082] In an embodiment in which anode active material layers 221 are disposed on both of two opposing surfaces of the anode current collector 222 of the anode piece 22 along its thickness direction, and cathode active material layers 211 are disposed on both of two opposing surfaces of the cathode current collector 212 of the cathode piece 21 along its thickness direction, the anode winding starting end 2211 of each anode active material layer 221 may extend beyond the cathode winding starting end 2111 of the cathode active material layer 211 disposed opposite the anode active material layer 221 with the separator 23 interposed therebetween, in the direction opposite to the winding direction X.

[0083] When the negative electrode winding starting end 2211 of the negative electrode active material layer 221 extends beyond the positive electrode winding starting end 2111 of the positive electrode active material layer 211 in the direction opposite to the winding direction X of the wound electrode assembly 20, this helps to ensure that the positive electrode active material layer 211 is sufficiently covered by the negative electrode active material layer 221, thereby reducing the risk of lithium deposition in the electrochemical device 100.

[0084] As shown in FIGS. 2 to 4, the length by which the negative electrode winding starting end 2211 extends beyond the positive electrode winding starting end 2111 in the direction opposite to the winding direction X of the winding type electrode assembly 20 is 1 mm or more.

[0085] In other words, the length by which the negative electrode winding starting end 2211 of the negative electrode active material layer 221 extends beyond the positive electrode winding starting end 2111 of the positive electrode active material layer 211, which faces the negative electrode active material layer 221 in the direction opposite to the winding direction X, is 1 mm or more. That is, with respect to the distance L in the direction opposite to the winding direction X between the negative electrode winding starting end 2211 of the negative electrode active material layer 221 and the positive electrode winding starting end 2111 of the positive electrode active material layer 211, which is disposed opposite the negative electrode active material layer 221 with the separator 23 interposed therebetween, L≧1 mm. L may be 2 mm, 3 mm, 4 mm, 5 mm, etc.

[0086] If the length by which the negative electrode winding starting end 2211 exceeds the positive electrode winding starting end 2111 is 1 mm or more, this contributes to the positive electrode active material layer 211 being sufficiently covered by the negative electrode active material layer 221, and the risk of lithium deposition in the electrochemical device 100 can be reduced.

[0087] In some other embodiments, the positions of the negative electrode winding starting end 2211 and the positive electrode winding starting end 2111 may coincide.

[0088] 2 to 4 , in some embodiments, the outermost pole piece of the wound electrode assembly 20 is the negative electrode piece 22, and / or the innermost pole piece of the wound electrode assembly 20 is the negative electrode piece 22. The outermost pole piece of the wound electrode assembly 20 may be the negative electrode piece 22, and the innermost pole piece of the wound electrode assembly 20 may be the positive electrode piece 21. The outermost pole piece of the wound electrode assembly 20 may be the positive electrode piece 21, and the innermost pole piece of the wound electrode assembly 20 may be the negative electrode piece 22. Both the outermost pole piece and the innermost pole piece of the wound electrode assembly 20 may be the negative electrode piece 22.

[0089] As shown in FIG. 5 , in some embodiments, the case 10 includes a lid 11, a side wall 12, and a bottom wall 13, the side wall 12 being cylindrical, the electrochemical device 100 further includes an electrode terminal 40 and a positive current collecting member 50, the wound electrode assembly 20 includes a positive electrode tab 25, and the electrode terminal 40 is installed on the lid 11 and electrically connected to the positive electrode tab 25 via the positive electrode current collecting member 50.

[0090] The positive electrode tab 25 is electrically connected to the positive electrode current collector 212 of the positive electrode piece 21. The positive electrode tab 25 protrudes to one side of the positive electrode piece 21 in the extension direction along the winding center line F1, which extends in the width direction of the positive electrode piece 21. The positive electrode tab 25 and the positive electrode current collector 212 are installed separately and then integrally connected by a connection method such as welding or adhesive. The positive electrode tab 25 and the positive electrode current collector 212 may be integrally molded. The material of the positive electrode tab 25 may be the same as or different from the material of the positive electrode current collector 212. The number of positive electrode tabs 25 may be one or more. Here, "multiple" includes both two and more than two. In this embodiment, the dimension of the positive electrode tab 25 along the winding direction X is smaller than the dimension of the positive electrode current collector 212 along the winding direction X.

[0091] The bottom wall 13 is connected to one end of the side wall 12 along its axial direction, and the bottom wall 13 and the side wall 12 may be integrally formed, or may be installed separately and connected together by a connection method such as welding or adhesive. An opening 121 is formed in the other end of the side wall 12 facing the bottom wall 13 along its axial direction, and the lid 11 seals the opening 121, and the lid 11, side wall 12, and bottom wall 13 together form a storage space for storing the wound-type electrode assembly 20.

[0092] 5 , the electrode terminal 40 may be insulated from the lid 11. The positive electrode current collecting member 50 is a conductive member, and electrical connection between the positive electrode tab 25 and the electrode terminal 40 is achieved via the positive electrode current collecting member 50. The positive electrode current collecting member 50 may be welded to or in contact with the positive electrode tab 25. The positive electrode current collector 212 may be welded to or in contact with the electrode terminal 40. In this case, the negative electrode piece 22 may be electrically connected to the side wall 12 or the bottom wall 13.

[0093] When the electrode terminal 40 and the positive electrode tab 25 are electrically connected via the positive electrode current collecting member 50, this contributes to improving the stability of the electrical connection between the electrode terminal 40 and the positive electrode tab 25.

[0094] Continuing with reference to FIG. 5, in some embodiments, the electrochemical device 100 further includes a negative electrode current collecting member 60, the wound electrode assembly 20 includes a negative electrode tab 26, and the bottom wall 13 is electrically connected to the negative electrode tab 26 via the negative electrode current collecting member 60.

[0095] The negative electrode tab 26 is electrically connected to the negative electrode current collector 222 of the negative electrode piece 22. The negative electrode tab 26 protrudes to one side in the extension direction along the winding center line F1 of the negative electrode piece 22, and the extension direction of the winding center line F1 coincides with the width direction of the negative electrode piece 22. The negative electrode tab 26 and the negative electrode current collector 222 are installed separately and then integrally connected by a connection method such as welding or adhesive. The negative electrode tab 26 and the negative electrode current collector 222 may be integrally molded. The material of the negative electrode tab 26 may be the same as or different from the material of the negative electrode current collector 222. The number of negative electrode tabs 26 may be one or more. In this embodiment, the dimension of the negative electrode tab 26 along the winding direction X is smaller than the dimension of the negative electrode current collector 222 along the winding direction X.

[0096] The positive electrode tab 25 and the negative electrode tab 26 are located at opposite ends of the wound electrode assembly 20 along the winding center line F1.

[0097] The negative current collecting member 60 may be welded to or abutted against the negative tab 26. The negative current collecting member 60 may be welded to or abutted against the bottom wall 13.

[0098] If the bottom wall 13 and the negative electrode tab 26 are electrically connected via the negative electrode current collecting member 60, this contributes to improving the stability of the electrical connection between the negative electrode terminal and the negative electrode tab 26.

[0099] As shown in FIG. 6 , in some other embodiments, the positive electrode tab 25 may be electrically connected to the bottom wall 13 via a positive electrode current collecting member 50, and the negative electrode tab 26 may be electrically connected to the electrode terminal 40 via a negative electrode current collecting member 60.

[0100] As shown in FIG. 7 , in some embodiments, the case 10 includes a lid 11, a side wall 12, and a bottom wall 13, and the side wall 12 is cylindrical. The electrochemical device 100 further includes an electrode terminal 40 and a positive current collecting member 50. The positive electrode piece 21 further includes a positive current collector 212. The positive current collector 212 further includes a positive electrode coating region 2121 and a positive electrode tab region 2122. The positive electrode tab region 2122 is located at one end of the positive electrode current collector 212 in the width direction. The positive electrode active material layer 211 is disposed on the surface of the positive electrode coating region 2121. The positive electrode tab region 2122 is folded toward the winding center line F1 to form a first end surface 2123 of the wound electrode assembly 20. The electrode terminal 40 is disposed on the lid 11 and electrically connected to the first end surface 2123 via the positive electrode current collecting member 50.

[0101] The width direction of the positive electrode current collector 212 is parallel to the width direction of the positive electrode piece 21. The positive electrode tab region 2122 is a region on one side of the positive electrode current collector 212 along the width direction where the positive electrode active material layer 211 is not applied. When the positive electrode piece 21 is in an unfolded state, the dimension of the positive electrode tab region 2122 along the length direction of the positive electrode piece 21 is the same as the dimension of the positive electrode application region 2121 along the length direction of the positive electrode piece 21. When the positive electrode piece 21 is in a wound state, the length direction of the positive electrode piece 21 coincides with the winding direction X.

[0102] When the positive electrode piece 21 is in a wound state, the positive electrode tab region 2122 is bent toward the winding center line F1 in a flattening manner to form a first end surface 2123 that is relatively flat.

[0103] The positive current collecting member 50 may be welded to or abutted against the first end surface 2123. When the electrode terminal 40 is installed on the lid 11 and connected to the first end surface 2123 via the positive current collecting member 50, this contributes to increasing the connection area between the positive current collecting member 50 and the positive electrode piece 21, thereby improving the rate characteristics of the electrochemical device 100.

[0104] Continuing with reference to FIG. 7 , in some embodiments, the electrochemical device 100 further includes a negative electrode current collecting member 60, and the negative electrode piece 22 further includes a negative electrode current collector 222. The negative electrode current collector 222 includes a negative electrode coating region 2221 and a negative electrode tab region 2222. The negative electrode tab region 2222 is located at one end of the negative electrode current collector 222 in the width direction, the negative electrode active material layer 221 is installed on the surface of the negative electrode coating region 2221, and the negative electrode tab region 2222 is bent toward the winding center line F1 to form a second end surface 2223 of the wound electrode assembly 20, and the bottom wall 13 is connected to the second end surface 2223 via the negative electrode current collecting member 60.

[0105] The width direction of the negative electrode current collector 222 is parallel to the width direction of the negative electrode piece 22. The negative electrode tab region 2222 is a region on one side of the negative electrode current collector 222 along the width direction where the negative electrode active material layer 221 is not applied. When the negative electrode piece 22 is in an unfolded state, the dimension of the negative electrode tab region 2222 along the length direction of the negative electrode piece 22 is the same as the dimension of the negative electrode application region 2221 along the length direction of the negative electrode piece 22. When the negative electrode piece 22 is in a wound state, the length direction of the negative electrode piece 22 coincides with the winding direction X.

[0106] When the negative electrode piece 22 is in a wound state, the negative electrode tab region 2222 is bent toward the winding center line F1 in a flattened manner to form a relatively flat second end surface 2223. The first end surface 2123 and the second end surface 2223 are located at opposite ends of the winding electrode assembly 20 along the extension direction of the winding center line F1.

[0107] The negative current collecting member 60 may be welded to or abutted against the second end surface 2223. When the bottom wall 13 is connected to the second end surface 2223 via the negative current collecting member 60, this contributes to increasing the connection area between the negative current collecting member 60 and the negative electrode piece 22, thereby improving the rate characteristics of the electrochemical device 100.

[0108] As shown in FIG. 8, in some other embodiments, the first end surface 2123 may be electrically connected to the bottom wall 13 via a positive electrode current collecting member 50, and the second end surface 2223 may be electrically connected to an electrode terminal via a negative electrode current collecting member 60.

[0109] Of course, in some other embodiments, the wound electrode assembly 20 includes a negative electrode tab 26, which is electrically connected to the negative electrode current collector 222 of the negative electrode piece 22, and the negative electrode tab 26 is electrically connected to the electrode terminal 40 via the negative electrode current collector 222, and the positive electrode piece 21 includes a positive electrode current collector 212, which includes a positive electrode coating region 2121 and a positive electrode tab region 2122, and the positive electrode tab region 2122 is connected to the positive electrode collector. The positive electrode active material layer 211 is located at one end of the body 212 in the width direction, the positive electrode active material layer 211 is placed on the surface of the positive electrode application area 2121, the positive electrode tab area 2122 is folded toward the winding center line F1 to form a first end face 2123 of the wound electrode assembly 20, the first end face 2123 and the negative electrode tab 26 are arranged opposite each other along the extension direction of the winding center line F1, and the bottom wall 13 may be connected to the first end face 2123 via the positive electrode current collecting member 50.

[0110] The wound electrode assembly 20 includes a positive electrode tab 25, which is electrically connected to a positive electrode current collector 212 of the positive electrode piece 21. The positive electrode tab 25 is electrically connected to an electrode terminal 40 via the positive electrode current collector 212. The negative electrode piece 22 includes a negative electrode current collector 222. The negative electrode current collector 222 includes a negative electrode coating region 2221 and a negative electrode tab region 2222. The negative electrode tab region 2222 is located at one end of the negative electrode current collector 222 in the width direction. The negative electrode active material layer 221 is disposed on the surface of the negative electrode coating region 2221. The negative electrode tab region 2222 is bent toward the winding center line F1 to form a second end surface 2223 of the wound electrode assembly 20. The positive electrode tab 25 and the second end surface 2223 are disposed opposite each other along the extension direction of the winding center line F1. The bottom wall 13 may be connected to the second end surface 2223 via a negative electrode current collector 60.

[0111] The present embodiment provides an electrical device that includes the electrochemical device 100 provided in any of the above embodiments.

[0112] The electrical device further includes an electrical body, and the electrochemical device 100 provides electrical energy to the electrical body.

[0113] The electric devices may be, but are not limited to, electronic devices, power tools, electric transportation, drones, and energy storage devices. The electronic devices may include smartphones, tablet computers, laptops, etc. The power tools may include electric drills, electric circular saws, etc. The electric transportation may include electric cars, electric motorcycles, electric bicycles, etc.

[0114] The above is only a preferred embodiment of the present application, and does not limit the present application. Those skilled in the art can make various modifications and changes to the present application. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present application are included in the protection scope of the present application.

Claims

1. 1. An electrochemical device comprising: A case with storage space inside, a wound electrode assembly accommodated in the accommodation space; the wound electrode assembly has a winding centerline, the wound electrode assembly includes a positive electrode piece and a negative electrode piece, the positive electrode piece includes a positive electrode active material layer, and the positive electrode active material layer has a positive electrode winding start end and a positive electrode winding end along the winding direction of the positive electrode piece, an electrochemical device in which, when viewed along the direction of the winding center line, a straight line that passes through the positive electrode winding end and is perpendicular to the winding center line is defined as a first reference line, a straight line that is perpendicular to the first reference line and is perpendicular to the winding center line is defined as a second reference line, and a straight line that passes through the positive electrode winding starting end and is perpendicular to the winding center line is defined as a third reference line, the third reference line and the second reference line form a zero angle or acute angle α, and 0°≦α≦30°.

2. 2. The electrochemical device of claim 1, wherein 0°≦α≦25°.

3. 2. The electrochemical device according to claim 1, wherein the wound electrode assembly has a central hole, the radius of the central hole is r, the radius of the wound electrode assembly is R, and r≧0.15R.

4. The electrochemical device comprises: (1) r≧0.3R; (2) r≦0.5R; (3) r≧1 mm; The electrochemical device according to claim 3 , wherein at least one of the following is satisfied:

5. The negative electrode piece includes a negative electrode active material layer, and the negative electrode active material layer has a negative electrode winding end and a negative electrode winding start end, and the electrochemical device is (1) along the winding direction of the wound electrode assembly, the winding end of the negative electrode exceeds the winding end of the positive electrode; (2) the negative electrode winding start end exceeds the positive electrode winding start end along the opposite direction to the winding direction of the wound electrode assembly; The electrochemical device according to claim 1 , wherein at least one of the following is satisfied:

6. The electrochemical device comprises: (1) The length by which the winding end of the negative electrode exceeds the winding end of the positive electrode along the winding direction of the wound electrode assembly is 1 mm or more; (2) The length by which the negative electrode winding start end exceeds the positive electrode winding start end along the direction opposite to the winding direction of the wound electrode assembly is 1 mm or more; The electrochemical device according to claim 5 , wherein at least one of the following is satisfied:

7. 2. The electrochemical device of claim 1, wherein the negative electrode piece is the outermost pole piece of the wound electrode assembly and / or the innermost pole piece of the wound electrode assembly.

8. The case includes a lid, a side wall, and a bottom wall, the side wall being cylindrical, and the electrochemical device is (1) The electrochemical device further includes an electrode terminal and a positive electrode current collecting member, the wound electrode assembly includes a positive electrode tab, and the electrode terminal is installed on the lid and electrically connected to the positive electrode tab via the positive electrode current collecting member; (2) The electrochemical device further includes a negative electrode current collecting member, the wound electrode assembly includes a negative electrode tab, and the bottom wall is electrically connected to the negative electrode tab via the negative electrode current collecting member; The electrochemical device according to claim 1 , wherein at least one of the following is satisfied:

9. The case includes a lid, a side wall, and a bottom wall, the side wall being cylindrical, and the electrochemical device is (1) The electrochemical device further includes an electrode terminal and a positive electrode current collecting member, the positive electrode piece further includes a positive electrode current collector, the positive electrode current collector includes a positive electrode coating area and a positive electrode tab area, the positive electrode tab area is located at one end of the positive electrode current collector in a width direction, the positive electrode active material layer is disposed on a surface of the positive electrode coating area, the positive electrode tab area is bent toward the winding center line to form a first end surface of the wound electrode assembly, and the electrode terminal is disposed on the cover and electrically connected to the first end surface via the positive electrode current collecting member; (2) The electrochemical device further includes a negative electrode current collecting member, the negative electrode piece further includes a negative electrode active material layer and a negative electrode current collector, the negative electrode current collector includes a negative electrode coating area and a negative electrode tab area, the negative electrode tab area is located at one end of the negative electrode current collector in a width direction, the negative electrode active material layer is installed on a surface of the negative electrode coating area, the negative electrode tab area is bent toward the winding center line to form a second end surface of the wound electrode assembly, and the bottom wall is electrically connected to the second end surface via the negative electrode current collecting member; The electrochemical device according to claim 1 , wherein at least one of the following is satisfied:

10. An electrical device comprising the electrochemical device according to any one of claims 1 to 9.

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